Sunspots cycle may be on the downswing

[BethesdaWX]

Hockeysticks are flying everywhere tonight, I'm having a hard time containing laughter...must be a new record. Indeed, the Hockeystick Is used in the 2007 and 2000 IPCC reports, was re-issued in the 2007 report, has more of a "sexy" look to it, but its the same thing. Hey if you guys don't trust me, look for yourself, I'll post all of it tomorrow. The graphs posted this evening are derivations from the same proxy subgroup & analysis. I don't want to get off topic here, so Tomorrow I'll post a thread on the whole Hockeystick Derivation & processing analysis, but for now, I'm going to use reconstructions that actually make sense.

In getting to more reliable reconstructions, knowing that: 1) Volcanism is a 2-3yr thing at most per eruption, and 2) TSI cannot account for the warming and cooling seens throughout the Holocene, speaks loudly. Using higher resolution proxies that extend back farther in a region basis can hit it gold, such as Ice Cores from Both Poles, and Sediment Cores. The CLOUD project is being completed by a huge interdisciplinary team of Scientists from around the world, comprised of atmospheric physicists, solar physicists, and cosmic-ray and particle physicists, to name a few. One good thing about this field is that it directly involves Paleoclimatology.

And Looking Longer Term

Bulgaria:

Institute for Nuclear Research and Nuclear Energy, Sofia

<LI>Austria:

University of Innsbruck, Institute of Ion Physics and Applied Physics

University of Vienna, Institute for Experimental Physics

<LI>Estonia:

University of Tartu, Department of Environmental Physics

<LI>Finland:

Helsinki Institute of Physics and University of Helsinki, Department of Physics

Finnish Meteorological Institute, Helsinki

University of Kuopio, Department of Physics

Tampere University of Technology, Department of Physics

<LI>Germany:

Goethe-University of Frankfurt, Institute for Atmospheric and Environmental Sciences

Leibniz Institute for Tropospheric Research, Leipzig

<LI>Portugal:

University of Lisbon, Department of Physics

<LI>Russia:

Lebedev Physical Institute, Solar and Cosmic Ray Research Laboratory, Moscow

<LI>Switzerland:

CERN, Physics Department

Fachhochschule Nordwestschweiz (FHNW), Institute of Aerosol and Sensor Technology, Brugg

Paul Scherrer Institute, Laboratory of Atmospheric Chemistry

<LI>United Kingdom:

University of Leeds, School of Earth and Environment

University of Reading, Department of Meteorology

Rutherford Appleton Laboratory, Space Science Department

<LI>United States:

California Institute of Technology, Division of Chemistry and Chemical Engineering

Now as for a response, a few individual responses.

This is blatantly false. Here is a list of Pinatubo sized eruptions that occurred 1580-1660:

Long Island Papua New Guinea 1660

Kolumbo 1650

Huayaputina 1600

Billy Mitchell 1580

All four of these eruptions were AT LEAST as large as Pinatubo and also occurred in the tropics. That's 4 VEI 6s in 80 years. In the last 80 years we have only had one VEI 6 (Pinatubo).

Irrelavent given the timeframe that a volcanic eruption can influence the climate. Volcanism Is NOT a viable explanation, neither is TSI. The Coldest Period of the LIA did not coincide with these eruptions.

Although its clear there is an effect, that much is true, but not enough to explain the Trend Down from the MWP over a 300yr SPan, and then the Spike up to Our Current Warm Era.

[skierinvermont]

I also wonder if the cumulative effect of all those VEI 5s in a relatively short time had an effect well beyond the simple magnitude of the individual eruptions. There may have been some feedback mechanisms in place that put the effects beyond the number of eruptions and their magnitudes.

Yes absolutely.. volcanoes never really reach their maximum potential cooling effect because it takes a long time to cool the earth off. By the time the earth begins to cool, the SO2 has dissipated. With a large enough eruption, or with consecutive eruptions, there will still be lots SO2 in the atmosphere even after the earth has cooled. If you could maintain the peak levels of SO2 in the atmosphere following Pinatubo... we might have cooled 2C instead of just .5C. As it is, by the time we had cooled .5C most of the SO2 had dissipated and the earth began gaining energy again.

You can also start to activate feedbacks like declining GHG concentrations and increased albedo if it gets cool enough.

2 Pinatubos in short succession would have over 2X the effect of a single Pinatubo.

Ever hear of Toba catastrophe theory? Toba was so big that the cooling lasted a lot longer.

[skierinvermont]

That's fine what you said, and I didn't even bother to check it, but it does not even come close to explaining the LIA. Its an intra-decadal scale type change. Not even close to a multi-century type drop in global temps.

I'm not saying, and neither does the IPCC, that it explains ALL or even most of the LIA. But it does explain something like .1 or .15C of the total .4 or .5C drop from the MWP during the cool period 1480-1700. This is based on feeding SO2 reconstructions into models which can accurately simulate the effect of modern volcanoes like Pinatubo.

[ORH_wxman]

I'm not saying, and neither does the IPCC, that it explains ALL or even most of the LIA. But it does explain something like .1 or .15C of the total .4 or .5C drop from the MWP during the cool period 1480-1700. This is based on feeding SO2 reconstructions into models which can accurately simulate the effect of modern volcanoes like Pinatubo.

What do you think explains the minimum of 0.5C drop during the LIA (and possibly more than that).

[skierinvermont]

What do you think explains the minimum of 0.5C drop during the LIA (and possibly more than that).

I'd say the ~.3C drop from MWP (1000-1480) to LIA (1480-1700) was like 75% TSI decrease and 25% volcano increase just eyeballing the RF derived from the SO2 and TSI reconstructions.

I agree the MWP to LIA was more than .3C peak to trough but I was just comparing 1000-1480 vs 1480-1700.

[ORH_wxman]

I'd say the ~.3-.4C drop from MWP (1000-1480) to LIA (1480-1700) was like 75% TSI decrease and 25% volcano increase just eyeballing the RF derived from the SO2 and TSI reconstructions.

I agree the MWP to LIA was more than .3 -.4C peak to trough but I was just comparing 1000-1480 vs 1480-1700.

How can you possibly contribute TSI contribution of several tenths before 1650 in like a 300-400 year period then staying until the late 1800s despite TSI not supporting those temps? That seems ridiculous in my book, and I would think you should too once stepping back a second.You cannot say volcanism either because that is less than a decadal scale.

[skierinvermont]

How can you possibly contribute TSI contribution of several tenths before 1650 in like a 300-400 year period then staying until the late 1800s despite TSI not supporting those temps? That seems ridiculous in my book, and I would think you should too once stepping back a second.You cannot say volcanism either because that is less than a decadal scale.

I'm not quite sure what you're saying?

All you have to do is look at the graph... the models a pretty simplistic... the SO2 levels and TSI levels create radiative forcing in the models which accurately reproduce the temperature reconstructions. They use the same physics by which we accurately simulate present volcanoes like Pinatubo. There was warmth in the 1700s due to the higher solar activity and lower volcanic activity. It was generally cool from 1480-1700 and 1800-1900 due to low solar activity. There were pronounced cold periods when these low solar periods coincided with high volcanic periods 1480-1500, 1580-1605, 1660-1700, 1805-1845, 1880s.

Volcanoes effect may occur only over 5 years, however it mathematically that would lower the mean temperature over a 10 or 20 year period by a significant amount. If you start getting 3,4,5 of such volcanoes over a few decades, it makes a significant difference in the average temperature. Pinatubo lowered the 90s temps by .07C... mathematically that means it lowered the last 40 years by .02C. If we had 4 Pinatubos, we're talking about close to .1C of volcano induced cooling once you account for feedbacks.

[ORH_wxman]

I'm not quite sure what you're saying?

All you have to do is look at the graph... the models a pretty simplistic... the SO2 levels and TSI levels create radiative forcing in the models which accurately reproduce the temperature reconstructions. There was warmth in the 1700s due to the higher solar activity and lower volcanic activity. It was generally cool from 1480-1700 and 1800-1900 due to low solar activity. There were pronounced cold periods when these low solar periods coincided with high volcanic periods 1480-1500, 1580-1605, 1660-1700, 1805-1845, 1880s.

You are being quite simplistic. The volcanic stuff is rarely a factor unless its VEI 6 which even then only last a couple to 3-4 years at most (and that is pushing it). TSI has already been shown by climate models to be a "minimal" impact. The LIA cannot be explained simply by TSI and volcanic activity, so the question remains as is...what in the sam hell caused the LIA? Its a rhetorical question....you cannot answer it and neither can climate scientists. We have theories and our own beliefs, but nobody has ever come up with a great reason. Solar has always been at the root of it, but obviously TSI doesn't do it. This is where the multi-decadal low solar activity comes in and why there is some research going on. But obviously a lot of research needs to be done.

I think its interesting personally. Maybe you do not and think its just some conspiracy to prove AGW wrong. I'm a skeptic by nature whenever I hear "the science is settled". I remember hearing that about snowstorms once and how the only way to get them was when the NAO was negative....but obviously that was a farce. Obviously that wasn't a controversial topic since it doesn't affect government policy, but its just an example of sketpicism. Global warming exists but I think we have the right to ask questions about how it evolved without receiving condecending answers.

[A-L-E-X]

You are being quite simplistic. The volcanic stuff is rarely a factor unless its VEI 6 which even then only last a couple to 3-4 years at most (and that is pushing it). TSI has already been shown by climate models to be a "minimal" impact. The LIA cannot be explained simply by TSI and volcanic activity, so the question remains as is...what in the sam hell caused the LIA? Its a rhetorical question....you cannot answer it and neither can climate scientists. We have theories and our own beliefs, but nobody has ever come up with a great reason. Solar has always been at the root of it, but obviously TSI doesn't do it. This is where the multi-decadal low solar activity comes in and why there is some research going on. But obviously a lot of research needs to be done.

I think its interesting personally. Maybe you do not and think its just some conspiracy to prove AGW wrong. I'm a skeptic by nature whenever I hear "the science is settled". I remember hearing that about snowstorms once and how the only way to get them was when the NAO was negative....but obviously that was a farce. Obviously that wasn't a controversial topic since it doesn't affect government policy, but its just an example of sketpicism. Global warming exists but I think we have the right to ask questions about how it evolved without receiving condecending answers.

Will, can't there be some other astronomical reasons also? I know that certain things such as precession of the earth's axes and cyclical variations in the orbit as well as when perihelion and aphelion occur have been attributed to the great ice ages.

[skierinvermont]

You are being quite simplistic. The volcanic stuff is rarely a factor unless its VEI 6 which even then only last a couple to 3-4 years at most (and that is pushing it). TSI has already been shown by climate models to be a "minimal" impact.

That is not what climate models say.

Climate models say that the fluctuations in TSI from MWP to LIA caused significant cooling. The peaks and troughs were caused by volcanic variability superimposed on solar variability.

Climate models accurately simulate temperature reconstructions using accepted TSI and volcanic radiative forcing reconstructions.

Everybody seems to agree that radiative forcing from TSI was .2W/m2 lower in the LIA than the MWP. According to climate models this must cause significant cooling. This is just basic physics. A radiative forcing of .2W'm2 must cause significant temperature change. So unless you are saying the TSI reconstructions are wrong you must accept that TSI caused significant cooling in the LIA.

One thing that needs to be clear here is that even though from peak to trough the MWP might have been .6-.8C warmer than the LIA, the MWP overall (1000-1480) was only .2-.3C warmer than the LIA (1480-1700). The peaks and troughs are caused by volcanic activity.

[ORH_wxman]

That is not what climate models say.

Climate models say that the fluctuations in TSI from MWP to LIA caused significant cooling. The peaks and troughs were caused by volcanic variability superimposed on solar variability.

Climate models accurately simulate temperature reconstructions using accepted TSI and volcanic radiative forcing reconstructions.

Everybody seems to agree that TSI was .2W/m2 lower in the LIA than the MWP. According to climate models this must cause significant cooling.

One thing that needs to be clear here is that even though from peak to trough the MWP might have been .6-.8C warmer than the LIA, the MWP overall (1000-1480) was only .2-.3C warmer than the LIA (1480-1700). The peaks and troughs are caused by volcanic activity.

You have a lot of faith in the Mann type reconstruction based on these comments. That is fine, but you act like it is settled. That is not true at all. Moberg and Loehle have average running temps of well over 0.5C difference. Many believe (and with good cause) that the difference between the LIA and modern temps (and MWP temps) are more than 0.3 or 0.4C. That's just something we cannot prove at this point. You believe the lesser difference, I believe the larger differences (not the largest, but over the 50% larger sides). You are more on the Mann side of the lesser difference. That is fine. I believe there was more of a difference. We can exchange peer review crap all day in either direction.

[skierinvermont]

You have a lot of faith in the Mann type reconstruction based on these comments. That is fine, but you act like it is settled. That is not true at all. Moberg and Loehle have average running temps of well over 0.5C difference. Many believe (and with good cause) that the difference between the LIA and modern temps (and MWP temps) are more than 0.3 or 0.4C. That's just something we cannot prove at this point. You believe the lesser difference, I believe the larger differences (not the largest, but over the 50% larger sides). You are more on the Mann side of the lesser difference. That is fine. I believe there was more of a difference. We can exchange peer review crap all day in either direction.

Actually I think the Moberg 2005 is a pretty good compromise and I like their methodology. I think Loehle has been pretty discredited for some very good reasons.

I'm not talking about the running 10 or 30 year mean.. I'm talking about the average temp across the whole MWP (1000-1480) vs LIA (1480-1700). The difference even on Moberg appears to be .25-.3C to me. Peak to trough it is much more like .8C.

Moberg was actually one of the reconstructions I was basing my original comments on.

You can take just about any modern climate model, feed in a modern SO2 reconstruction and a modern TSI reconstruction for the last 1,000 years, and it will accurately simulate the Moberg 2005 reconstruction using only TSI, SO2, and physics.

[ORH_wxman]

Actually I think the Moberg 2005 is a pretty good compromise and I like their methodology. I think Loehle has been pretty discredited for some very good reasons.

I'm not talking about the running 10 or 30 year mean.. I'm talking about the average temp across the whole MWP (1000-1480) vs LIA (1480-1700). The difference even on Moberg appears to be .25-.3C to me. Peak to trough it is much more like .8C.

Moberg was actually one of the reconstructions I was basing my original comments on.

You can take just about any modern climate model, feed in a modern SO2 reconstruction and a modern TSI reconstruction for the last 1,000 years, and it will accurately simulate the Moberg 2005 reconstruction using only TSI, SO2, and physics.

You are not being homogeneous with the typical temperature changes. You want to claim that volcanism and TSI were good for the LIA but yet refuse to act as if the 30 year mean doesn't matter when these changes are supposed to be on a scale less than that when we talk about more present temps. Most reconstructions have the peak to valley near 1C...what caused that? It cannot be explained by what you claim. Again its a rhetorical question. You can't explain it and neither can scientists....its why we are sitting having these debates in the first place. If it was so easy to explain these differences, we wouldn't be sitting here. We have plenty of theories, but nothing concrete. Again, theory is theory.

[tacoman25]

A few points:

1. Even though the effect on temperature lasts only 3-5 years or so, you basically are lowering temperature by .2-.5C during this period and when you average that into a decade it makes a significant difference of up to .1C for a single volcano and more if you get 2 climate volcanoes in the space of 10 or 15 years. If you get 4 Pinatubos in a 30 year period, as we did from 1660-1700, that could have a total effect of .1-.2C on the period. The temperature reconstructions are not really precise enough to show that it was .3-.8C cooler for a few years and then warmer for the next few years. They just show that it was .1-.2C cooler for a few decades.

2. The SO2 reconstructions basically show multiple Pinatubos occurring in the periods 1480-1500, 1580-1605, 1660-1700, 1805-1845.

3. SO2 is not the only cause of coolness during these periods, all 4 of them also incidentally occurred in an already cool period due to low solar activity 1400-1600, 1650-1700 and 1780-1830. There was also high volcano activity in the late 1200s, but it didn't get as cold because there was high solar activity. So it's both. The general coolness from 1480-1700 probably would have been .1-.2C warmer without the high level of volcanoes.

4. These ARE normal climate models which they are then feeding in good SO2 and TSI reconstructions into. With solar alone they don't accurately reproduce temperatures. With volcanoes alone they don't either. With both, we get a pretty accurate simulation.

1. No, there were not "4 Pinatubos" in the 1660-1700 period. That is a blatant lie.

4. Climate models have continuously shown different results. There is absolutely nothing guaranteeing the models you currently prefer are correct. .3C of cooling seems pretty conservative considering the glacier advancement, etc that the earth saw during that period. Bottom line: like ORH, I don't like how you make these statements as if they are fact, when in actuality there is plenty of uncertainty.

[tacoman25]

You are being quite simplistic. The volcanic stuff is rarely a factor unless its VEI 6 which even then only last a couple to 3-4 years at most (and that is pushing it). TSI has already been shown by climate models to be a "minimal" impact. The LIA cannot be explained simply by TSI and volcanic activity, so the question remains as is...what in the sam hell caused the LIA? Its a rhetorical question....you cannot answer it and neither can climate scientists. We have theories and our own beliefs, but nobody has ever come up with a great reason. Solar has always been at the root of it, but obviously TSI doesn't do it. This is where the multi-decadal low solar activity comes in and why there is some research going on. But obviously a lot of research needs to be done.

I think its interesting personally. Maybe you do not and think its just some conspiracy to prove AGW wrong. I'm a skeptic by nature whenever I hear "the science is settled". I remember hearing that about snowstorms once and how the only way to get them was when the NAO was negative....but obviously that was a farce. Obviously that wasn't a controversial topic since it doesn't affect government policy, but its just an example of sketpicism. Global warming exists but I think we have the right to ask questions about how it evolved without receiving condecending answers.

Exactly, this is something that has been demonstrated by modern eruptions. There have been a number of VEI 5 eruptions in the last 100 years or so, and none of them had nearly the climate impact that VEI 6 Pinatubo had...and yet skiier claims all these VEI 5's in the LIA contributed just as much cooling as Pinatubo. It doesn't add up.

[skierinvermont]

1. No, there were not "4 Pinatubos" in the 1660-1700 period. That is a blatant lie.

4. Climate models have continuously shown different results. There is absolutely nothing guaranteeing the models you currently prefer are correct. .3C of cooling seems pretty conservative considering the glacier advancement, etc that the earth saw during that period. Bottom line: like ORH, I don't like how you make these statements as if they are fact, when in actuality there is plenty of uncertainty.

1. No it is not. There are 4 SO2 spikes in the 1660-1700 period the size of Pinatubo's SO2 spike. This could easily have lowered global temps in that period by .2C or more.

[skierinvermont]

Exactly, this is something that has been demonstrated by modern eruptions. There have been a number of VEI 5 eruptions in the last 100 years or so, and none of them had nearly the climate impact that VEI 6 Pinatubo had...and yet skiier claims all these VEI 5's in the LIA contributed just as much cooling as Pinatubo. It doesn't add up.

Because those VEI 5s had much larger SO2 footprints than Mount Saint Helens. Laki was only a VEI 4 and had an effect larger than Pinatubo's. It's all about SO2, and those VEI 5s have SO2 footprints as large as Pinatubo's.

Mount Saint Helens was mostly an ash eruption with very little SO2. El Chichon had a decent amount of SO2 even though it was only VEI 5 and so caused a couple tenths of cooling.

It's also worth noting that Pinatubo was a low end 6. El Chichon was a fairly low end 5 and yet had a climate effect of half of Pinatubo. Laki was a 4 and had a climate impact greater than Pinatubo. It's possible for 4s to have higher impacts than Pinatubo and it's very easy for 5s to. Pinatubo was relatively low SO2 content.

[skierinvermont]

You are not being homogeneous with the typical temperature changes. You want to claim that volcanism and TSI were good for the LIA but yet refuse to act as if the 30 year mean doesn't matter when these changes are supposed to be on a scale less than that when we talk about more present temps. Most reconstructions have the peak to valley near 1C...what caused that? It cannot be explained by what you claim. Again its a rhetorical question. You can't explain it and neither can scientists....its why we are sitting having these debates in the first place. If it was so easy to explain these differences, we wouldn't be sitting here. We have plenty of theories, but nothing concrete. Again, theory is theory.

I'm using a ruler and lining it up on my computer screen and the peak to trough on Moberg 2005, which I believe is a preferable reconstruction even though it shows more variability than most others, is .6C for the 30 year mean. Not even close to 1C.

I believe, based on what scientists have said and what the computer model simulations show, that the peak to trough can be explained by about .3C of long-term solar cooling during the 1480-1700 period, and an additional .2-.3C of volcanic cooling during the 1580-1606 and 1660-1700 periods which are the two coldest on the Moberg reconstruction.

The general cooling of .3C during the 1480-1700 period is explained mostly by the low solar activity with some contribution from the high volcanic activity.

Scientists can explain the global temperature variations of the last 1,000 years to a reasonable degree. There is of course some uncertainty in exactly what the temperatures were and some uncertainty about the TSI and volcano reconstructions, but by and large TSI and volcanoes lead to a satisfactory explanation of temperature. There is not some gaping whole in our knowledge as you are claiming. At least not in the opinions of actual scientists which you haven't given me any good reason to doubt.

IPCC 2007:

Various simulations of NH (mean land and marine) surface temperatures produced by a range of climate models, and the forcings that were used to drive them, are shown in Figure 6.13. Despite differences in the detail and implementation of the different forcing histories, there is generally good qualitative agreement between the simulations regarding the major features

...

All of these simulations, therefore, appear to be consistent with the reconstructions of past NH temperatures, for which the evidence (taken from Figure 6.10c) is shown by the grey shading underlying the simulations inFigure 6.13d.

We are having this conversation because you either unaware of this conclusion in IPCC 2007, or you find reason to disagree with it (I do not believe you have presented any such reason).

[CT Rain]

I'm using a ruler and lining it up on my computer screen and the peak to trough on Moberg 2005, which I believe is a preferable reconstruction even though it shows more variability than most others, is .6C for the 30 year mean. Not even close to 1C.

I believe, based on what scientists have said and what the computer model simulations show, that the peak to trough can be explained by about .3C of long-term solar cooling during the 1480-1700 period, and an additional .2-.3C of volcanic cooling during the 1580-1606 and 1660-1700 periods which are the two coldest on the Moberg reconstruction.

The general cooling of .3C during the 1480-1700 period is explained mostly by the low solar activity with some contribution from the high volcanic activity.

Wasn't the true Maunder Minimum between 1645 and 1715?

With virtually no solar activity, volcanic activity (with the potential of high SO2 emissions), and possibly regional multi-decadal climate patterns (i.e. a significant -NAO for a number of years??) you could see a dramatic amount of cooling over a certain region (i.e. northern Europe) over that 70 year period.

The impact on the rest of the globe and how much cooling came from which forcing is going to be next to impossible to establish imo during the MM.

If we do enter a multi-decadal period of very low solar activity maybe the impact of AGW would be muted somewhat I'd imagine.

[skierinvermont]

Wasn't the true Maunder Minimum between 1645 and 1715?

With virtually no solar activity, volcanic activity (with the potential of high SO2 emissions), and possibly regional multi-decadal climate patterns (i.e. a significant -NAO for a number of years??) you could see a dramatic amount of cooling over a certain region (i.e. northern Europe) over that 70 year period.

The impact on the rest of the globe and how much cooling came from which forcing is going to be next to impossible to establish imo during the MM.

If we do enter a multi-decadal period of very low solar activity maybe the impact of AGW would be muted somewhat I'd imagine.

Well the true Maunder is 1645-1715 yes, but there was fairly low solar activity back to 1450 as well. The period of low solar activity was generally cool, but the coldest periods occurred when there were multiple eruptions in a short period with the SO2 content of Pinatubo.

[WeatherRusty]

Wasn't the true Maunder Minimum between 1645 and 1715?

With virtually no solar activity, volcanic activity (with the potential of high SO2 emissions), and possibly regional multi-decadal climate patterns (i.e. a significant -NAO for a number of years??) you could see a dramatic amount of cooling over a certain region (i.e. northern Europe) over that 70 year period.

The impact on the rest of the globe and how much cooling came from which forcing is going to be next to impossible to establish imo during the MM.

If we do enter a multi-decadal period of very low solar activity maybe the impact of AGW would be muted somewhat I'd imagine.

The black body temperature response for the whole Earth (Planck Equation , Stephan Boltzmann Law) to a quiet Sun amounts to less than 0.1C when the difference between a quiet Sun and a current day active Sun is generously given 0.25W/m^2 forcing.

The same formula which gives 1.2C of warming per 3.7W/m^2 forcing for a doubling of CO2 applies to solar forcing.

3.7W/15=~0.25W

1.2C/15=0.08C

That's why climate scientists don't afford the intrinsic variability of the Sun much impact on Earth's climate. It's why we measure about 0.1C temperature variation between typical modern max and min.

[coldlover]

Hi i dont know much about this topic but does this have any effect on winters coming?

[CT Rain]

Well the true Maunder is 1645-1715 yes, but there was fairly low solar activity back to 1450 as well. The period of low solar activity was generally cool, but the coldest periods occurred when there were multiple eruptions in a short period with the SO2 content of Pinatubo.

Which makes sense. Especially if you couple all of the above with some time of other multi-decadal variable such as a -NAO (which would dramatically alter the temps in northern europe where the 'mini ice age' occurred.)

[CT Rain]

The black body temperature response for the whole Earth (Planck Equation , Stephan Boltzmann Law) to a quiet Sun amounts to less than 0.1C when the difference between a quiet Sun and a current day active Sun is generously given 0.25W/m^2 forcing.

The same formula which gives 1.2C of warming per 3.7W/m^2 forcing for a doubling of CO2 applies to solar forcing.

3.7W/15=~0.25W

1.2C/15=0.08C

That's why climate scientists don't afford the intrinsic variability of the Sun much impact on Earth's climate. It's why we measure about 0.1C temperature variation between typical modern max and min.

Besides a radiative transfer argument it's possible changes in solar activity have more influence on the earth's climate than just a change in radiative forcing. Whether that's changes in the stratosphere or what I don't know.

[skierinvermont]

Which makes sense. Especially if you couple all of the above with some time of other multi-decadal variable such as a -NAO (which would dramatically alter the temps in northern europe where the 'mini ice age' occurred.)

Well the temperature drops did extent beyond Europe but we really only have good data for the NH. And it's important to remember temperature variations for the NH are usually larger because the land % is greater.

[LakeEffectKing]

Wasn't the true Maunder Minimum between 1645 and 1715?

With virtually no solar activity, volcanic activity (with the potential of high SO2 emissions), and possibly regional multi-decadal climate patterns (i.e. a significant -NAO for a number of years??) you could see a dramatic amount of cooling over a certain region (i.e. northern Europe) over that 70 year period.

The impact on the rest of the globe and how much cooling came from which forcing is going to be next to impossible to establish imo during the MM.

If we do enter a multi-decadal period of very low solar activity maybe the impact of AGW would be muted somewhat I'd imagine.

However, if (and if all other known climate factors remaining fairly normal) we do see a sizable reduction in solar activity and a corresponding sizable global reaction (like, maybe slightly downward), the AGW hypothesis would have to be thrown out and/or retooled. A larger degree of solar forcing on the previous decades' temp increase would HAVE to be figured in, with respect to the historical global temperature recipe, thus reducing/eliminating the correlation between +CO2 -> +T.

[tacoman25]

1. No it is not. There are 4 SO2 spikes in the 1660-1700 period the size of Pinatubo's SO2 spike. This could easily have lowered global temps in that period by .2C or more.

Based on proxies that are very limited compared to the data we have for Pinatubo. Given the data we have from the 20th century, it seems very unlikely that any VEI 5 (much less several consecutive ones) would produce the kind of global cooling that Pinatubo did. The eruption in the early 1800s was a VEI 7 and the cooling from that is much more verifiable and consistent with what we know about volcanic eruptions.

[tacoman25]

Because those VEI 5s had much larger SO2 footprints than Mount Saint Helens. Laki was only a VEI 4 and had an effect larger than Pinatubo's. It's all about SO2, and those VEI 5s have SO2 footprints as large as Pinatubo's.

Mount Saint Helens was mostly an ash eruption with very little SO2. El Chichon had a decent amount of SO2 even though it was only VEI 5 and so caused a couple tenths of cooling.

It's also worth noting that Pinatubo was a low end 6. El Chichon was a fairly low end 5 and yet had a climate effect of half of Pinatubo. Laki was a 4 and had a climate impact greater than Pinatubo. It's possible for 4s to have higher impacts than Pinatubo and it's very easy for 5s to. Pinatubo was relatively low SO2 content.

Laki was a VEI 6. I don't know of any VEI 5 or lower that had an effect similar to or surpassing Pinatubo's.

[tacoman25]

The black body temperature response for the whole Earth (Planck Equation , Stephan Boltzmann Law) to a quiet Sun amounts to less than 0.1C when the difference between a quiet Sun and a current day active Sun is generously given 0.25W/m^2 forcing.

The same formula which gives 1.2C of warming per 3.7W/m^2 forcing for a doubling of CO2 applies to solar forcing.

3.7W/15=~0.25W

1.2C/15=0.08C

That's why climate scientists don't afford the intrinsic variability of the Sun much impact on Earth's climate. It's why we measure about 0.1C temperature variation between typical modern max and min.

This doesn't add up even with skiier's conservative .3C estimate due to solar cooling during the Maunder Minimum...why do most climate models demonstrate way more than .1C of cooling due to solar during that time period?

[tacoman25]

Which makes sense. Especially if you couple all of the above with some time of other multi-decadal variable such as a -NAO (which would dramatically alter the temps in northern europe where the 'mini ice age' occurred.)

One thing to consider, though, is that volcanic eruptions often have very regional effects on temperature (though huge ones that occur near the equator like Pinatubo have more global temperature effects). So while massive eruptions like Laki in 1783 caused severe coolling in parts of the NH (since it occurred on Iceland), it wouldn't have had nearly the same global effects. Globally, most evidence indicates that 1650-1715 was the coldest period of the Little Ice Age, and this was also the time that the sun was deadest. Volcanic eruptions may or may not have had significant regional effects during this time period, but they probably were not a significant factor in global cooling.